Optical Engineering

In this issue devoted to Infrared Astronomy Instruments, you will note that most of the instruments are designed for use at altitude, either in aircraft, balloons, probes or satellites. Such usage permits observation above the interfering atmosphere usually encountered during ground observations. Most of the water vapor is below the platform at 40,000 feet (~13 km) and most of the CO2 is below platforms at 120,000 feet (~40 km).